Catamaran stabilizer

ABSTRACT

A free-surface stabilizing tank for a catamaran-like structure. The catamaran is defined by a pair of buoyant bodies lying side by side, joined together by a deck plate. The free-surface tank is defined by the two adjacent walls of the bodies and a bottom plate lying below the surface of the water and, like the deck plate, joining the two buoyant bodies. The bottom plate is positioned so as to be above the water level when the catamaranlike structure is in transit and so as to be below the water level when the structure is in its working position.

0 United States Patent [151 3,653,354 Pangalila Apr. 4, 1972 [5 CATAMARAN STABILIZER References Cited [72] Inventor: Frans V. A. Pangalila, Matawan UNITED STATES PATENTS Township, NJ. 3,447,502 6/1969 Leopold ..114/61 [73] ASs-ignee: Flume Stabilization systems, Inc. Wes 3,054,373 9/1962 Rlpley wood Primary Examiner-Trygve M. Blix [22] Filed: Mar. 2, 1970 Attorney-Fleit, Gipple & Jacobson Related US. Applicatio Data A free-surface stabilizing tank for a catamaran-like structure. The catamaran is defined by a pair of buoyant bodies lying [63] 282 ;313:5 of 850574 side by side, joined together by a deck plate. The free-surface tank is defined by the two adjacent walls of the bodies and a bottom plate lying below the surface of the water and, like the 2? deck plate, joining the two buoyant bodies. The bottom plate 114/61 0 5 0 5 D is positioned so as to be above the water level when the [5 C o are catamaran-like structure is in transit and so as to be below the water level when the structure is in its working position.-

5 Claims, 2 Drawing Figures PATENTEU APR 4 I972 INVENTOR F RANS V. A.

PANGALILA CATAMARAN STABILIZER This application is a continuation-in-part of application Ser. No. 850,574, filed Aug. 15, 1969 now abandoned.

BACKGROUND OF THE INVENTION As it relates to the present invention, a catamaran may be defined as a pair of independently floatable vessels positioned side by side and attached by means of a plate defining a deck structure above the surface of the water. The conventional semi-submersible platform falls into this general catagory and, as is well known, the uses for such a structure are unlimited.

In many of its applications, the catamaran must be maintained at a relatively stable position with respect to the floor of the associated waterway. It thus becomes necessary to provide some means by which the deck structure may be maintained in a horizontal state.

Recently, the free-surface stabilizing tank has been increasing in popularity. The reasons for this increase are many, but to name a few, its inexpensiveness, its simplicity and its effectiveness, appear paramount. As is well known, the free-surface tank operates in such a manner that a liquid is allowed to rush to and fro in the tank and, where there is a phase difference of 90 between the position of the liquid and the roll of the associated vessel, the liquid acts as a counter-force retarding roll and thus stabilizing the vessel. As is also well known, this 90 phase relationship may be attained by acting on one of numerous variables. For example, the dimensions of the tank and the level of the liquid housed therein may be varied, in a well known manner, so that the natural frequency of the tank is approximately equal to the natural frequency of the associated vessel. In this manner, the stabilizing effect of the tank is maximized.

Calculations have been made to determine the size of tank necessary for adequately stabilizing a typical catamaran. These calculations have indicated that the tank must be of a size approaching the size of the deck. Naturally, to provide such a tank would create numerous problems. The tank could not be positioned atop the deck since doing so would detract from substantially the entire deck area. To position the tank below the deck would also create problems. Such a tank would be expensive to construct in view of its large size and would require positioning so that the operation of the catamaran was not deleteriously affected.

SUMMARY OF THE INVENTION The present invention relates to a free-surface tank stabilizer for use in a catamaran-like structure, which stabilizer is simple in construction, is economical and is yet extremely effective in operation. The inventive stabilizer may be used in any application wherein there are positioned, side by side, a pair of elongated floating vertical bodies which are spaced apart a substantial distance and which require a stabilizing tank of large dimensions.

In the present invention, two ships or ship-like structures, defining what may be called a catamaran, are positioned side by side. These structures are joined together by means of a deck plate located above the surface of the water in which the catamaran floats. As is conventional, the deck is a work area for performing numerous functions depending upon the purpose for which the catamaran is used. In addition to the deck structure, another flat plate, termed a base plate, joins the pair of floating bodies, this base plate extending between the adjacent walls of the floating vertical bodies, and extending substantially the entire fore and aft dimensions of these bodies.

The base plate is affixed, horizontally oriented, at a predetermined height along the walls of the floating vertical bodies. This height is of importance and is chosen so that when the catamaran is in transit, the plate rides above the surface of the water in which the catamaran floats, and when the catamaran is in its operating positionits vertical members containing a substantial amount of ballast water-the plate rides below the surface of the water.

When the catamaran is in its operating position, with the base plate below the surface of the water, a stabilizing tank is defined. The bottom of the tank is defined by the base plate, the sides of the tank are defined by the adjacent vertical walls of the floating bodies, and the free surface of the tank is defined by the surface of the sea in which the structure floats. The tank of the present invention has no fore and aft walls.

When the structure of the present invention is in its operating position it rolls, and the sea water restrained between the adjacent walls of the vertical member and the sub-surface horizontal plate, flows freely between the adjacent vertical walls. When the extent of the horizontal plate and its distance below the surface of the sea is proper, the sea water constrained in the tank of the present invention flows to and fro in such a manner that the position of the water is substantially out of phase with respect to the roll of the vessel. In such a manner, the catamaran structure is stabilized. The depth of water in the free-surface stabilizer forming a part of the present invention can easily be adjusted by simply ballasting or deballasting the tanks defined by the floating vertical bodies. In this manner, the phase may be adjusted.

By employing the tank of the present invention, the catamaran-like structure is stabilized inexpensively and yet effectively without detracting from the workable area on the deck of the structure. Further, the position of the horizontal plate, which is submerged to provide stability during drilling operations and defines the bottom of the tank, permits the structure to be easily moved about by removing sufficient ballast from the twin floating bodies that the plate rides above the surface of the water.

Accordingly, it is the main object of the present invention to provide a catamaran stabilizer of the passive tank variety, which stabilizer is simple in design, economical in construction, and effective in operation.

It is another object of the present invention to provide a free-surface stabilizer for a catamaran-like structure which efficiently stabilizes the catamaran when in its operating position and yet does not detract from the portability of the structure when in transit.

These and other objects of the invention, as well as many of the attendant advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a typical, in transit, catamaran constructed in accordance with the teachings of the present invention; and

FIG. 2 is a cross-sectional view of the stabilized catamaran of the present invention, taken along line 2-2 of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS With reference to Figures 1 and 2, a typical catamaran is shown at 10 and is equipped with a stabilizing tank constructed in accordance with the present invention. The tank is shown generally at 12. The catamaran 10 is defined by a pair of displacement members 14 and 16, respectively. Members 14 and 16 are hollow and thus serve to displace an amount of water sufficient to cause the structure 10 to float. Connecting the members 14 and 16 is a deck structure 18 which, when the catamaran l0 floats, lies above the water level.

The displacement members 14 and 16 are supported by pitch must be reduced to a minimum in order that the safety of the shaft 22 is ensured. The present invention eliminates much of the pitch dangerous to the machinery used in various operations carried out by conventional semi-submersible platforms, or catamarans.

The present invention embodies itself in a flat sub-surface horizontal plate positioned between the displacement members 14 and 16. More particularly, a plate 24 is secured to a wall 26 of member 14 and to a wall 28 of member 16. The plate 24 is attached to the adjacent walls 26 and 28 at a point so that it is below the surface of the water in which the catamaran floats when the members 14 and 16 are flooded during drilling operations, but sits above the surface of the water when the members 14 and 16 have been appropriately evacuated of ballast for transit. Plate 24 defines the bottom of a free-surface stabilizing tank, the end walls 26 and 28 define the end walls of'this tank, and the surface of the associated body of water defines the free-surface of this tank. The tank has no side walls.

The operation of the catamaran stabilizer of the present invention is best explained with reference to Figure 2. The catamaran 10, due to the displacement members 14 and 16, floats so that the deck 18 is substantially above the surface of the water. Due to wave action, the catamaran has a tendency to roll from side to side, but when the structure begins to roll, the water restrained by the adjacent walls 26 and 28 and by the horizontal plate 24 flows to and fro. When the plate 24 is properly positioned and dimensioned, a bore 30 comes into being, this bore cyclically travelling between walls 26 and 28. The bore travels in such a way that its position is 90 out of phase with the roll of the catamaran 10. For example, the bore will be in the position shown in dotted lines when the catamaran is in the position shown in Figure 2, rolling in the direction of the arrow 32. In this manner, maximum stabilization results.

As seen best in Figure 1, when a sufficient amount of sea water is removed from the tanks defined by the vertical members l4 and 16, placing the catamaran in its transit mode, the base plate 24 rides above the surface of the water in which the catamaran floats. This ensures that the catamaran experiences no drag from the base plate 24. Naturally, this is important when one realizes that the speed of a vessel and its fuel consumption are related to the drag exhibited by the vessel.

Above, the present invention has been described with reference to a pair of displacement members in the form of hollow elongated walls. it should be understood, however, that the displacement members can take many forms just so long as they are defined by vertical walls such as 26 and 28 which define a stabilizing tank. For example, rather than employing members 14 and 16, a pair of ships may be provided. Generally, the present invention is applicable whenever stabilization is required, but the size of a useful stabilizing tank is excessive. it is the intent, therefore, that the present invention not be limited by the above, but be limited only as defined in the appended claims.

I claim:

1. A method of stabilizing a semi-submersible floating body comprising a first buoyant body having'an elongated vertical wall adapted to float in a body of water; a second buoyant body having an elongated vertical wall, which wall is spaced from and parallel to the vertical wall on said first buoyant body, water; a deck structure joining said first and said second bodies and adapted to lie above the surface of the water; and a flat horizontal plate extending a substantial distance along the length of said first and second buoyant bodies, the method comprising the steps of lowering said semi-submersible floating body into said body of water so that said plate lies beneath the surface of said body of water; trapping a substantial stabilizing body of water between said plate and said vertical walls; and positioning said plate so that it is below the surface of the water when said semi-submersible system is in its operatin mode an amountso that the trapped substantial stabilizing ody of water oscillates between said vertical walls substantially out of phase with the roll of said semi-submersible floating body.

2. The method as defined in claim 1 wherein said horizontal plate lies along substantially the entire length of said first and second buoyant bodies.

3. The method as defined in claim 1, wherein the vertical walls and the horizontal plate define a semi-enclosed free-surface stabilizing tank; wherein the roll of the semi-submersible body causes a bore to be defined by the water within the semienclosed tank; and wherein there exists a substantially 90 phase relationship between the position of the bore and the roll of the semi-submersible body.

4. The method as defined in claim 1, wherein said deck structure is sufficiently high above the surface of the water so that the vertical walls and the horizontal plate define a semienclosed free-surface tank wherein the water within the tank is in its free-surface state.

5. The method as defined in claim 1, wherein said first and second buoyant bodies serve as ballast tanks which either take on sea water or expel same depending upon whether the semisubmersible body is to be in its operating mode or its transit mode, respectively.

said second buoyant body adapted to float in a body of I 

1. A method of stabilizing a semi-submersible floating body comprising a first buoyant body having an elongated vertical wall adapted to float in a body of water; a second buoyant body having an elongated vertical wall, which wall is spaced from and parallel to the vertical wall on said first buoyant body, said second buoyant body adapted to float in a body of water; a deck structure joining said first and said second bodies and adapted to lie above the surface of the water; and a flat horizontal plate extending a substantial distance along the length of said first and second buoyant bodies, the method comprising the steps of lowering said semi-submersible floating body into said body of water so that said plate lies beneath the surface of said body of water; trapping a substantial stabilizing body of water between said plate and said vertical walls; and positioning said plate so that it is below the surface of the water when said semisubmersible system is in its operating mode an amount so that the trapped substantial stabilizing body of water oscillates between said vertical walls substantially 90* out of phase with the roll of said semi-submersible floating body.
 2. The method as defined in claim 1, wherein said horizontal plate lies along substantially the entire length of said first and second buoyant bodies.
 3. The method as defined in claim 1, wherein the vertical walls and the horizontal plate define a semi-enclosed free-surface stabilizing tank; wherein the roll of the semi-submersible body causes a bore to be defined by the water within the semi-enclosed tank; and wherein there exists a substantially 90* phase relationship between the position of the bore and the roll of the semi-submersible body.
 4. The method as defined in claim 1, wherein said deck structure is sufficiently high above the surface of the water so that the vertical walls and the horizontal plate define a semi-enclosed free-surface tank wherein the water within the tank is in its free-surface state.
 5. The method as defined in claim 1, wherein said first and second buoyant bodies serve as ballast tanks which either take on sea water or expel same depending upon whether the semi-submersible body is to be in its operating mode or its transit mode, respectively. 